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Daily maintenance strategy of UPS device in chemical industry

Mar 02, 2021

Daily maintenance strategy of UPS device in chemical industry

UPS power supply is widely used in the field of refining and chemical industry. As the power supply of the instrument DCS system, it provides guarantee for the operation of instrument equipment, which is related to the safety of production equipment. How to safely use the existing UPS power equipment, reduce the failure rate, and extend its service life is an important issue in the maintenance of chemical and electrical appliances.

In each control room of the chemical operation department, due to the particularity of production, according to the load's requirements for output stability, switching time, and output waveform, it is determined that all online UPSs are selected. The output stability and instant response of online UPS are better than online interactive and backup types, and it is also more adaptable to non-linear loads and inductive loads. In order to achieve uninterrupted power supply, UPS is also used in conjunction with generators.

At this stage, chemical and electrical maintenance has formulated detailed daily, monthly and annual inspection plans to meet the maintenance needs from the system requirements.

1. Daily inspection

(1) Observe the UPS display and control operation panel on the spot, confirm that the various graphic display units on the LCD panel are in normal operation, all the operating parameters of the power supply are within the normal value range, and there are no faults and errors in the displayed records. Alarm information.

(2) Check whether there are obvious signs of overheating.

(3) Observe the load carried by the UPS and whether there is any change in the battery backup time. If there is any change, check whether there is an increase in the load, the current operation of the load, and whether the load has unknown faults.

(4) Listen for suspicious changes in acoustic noise, and pay special attention to the noise of the input and output isolation transformers of the UPS power supply. When there is an abnormal "squeak", there may be poor contact or poor inter-turn winding insulation. When there is a low-frequency "cymbal sound", the transformer may be biased.

(5) Ensure that the filter screen of the exhaust fan at the back of the cabinet does not have any blockage.

(6) When the output voltage of the UPS is found to be abnormally high, check whether the filter capacitor of the UPS is intact?

(7) If the above is possible, record the inspection results in the team operation log to provide a basis for analyzing whether there is any obvious deviation from the normal operation state.

2. Monthly inspection

(1) Measure and record: the voltage of a single battery; the floating voltage value of the battery pack, the charging current of the battery; the input and output voltage of the UPS power supply, the input and output line current of the UPS power supply and other operating data.

(2) All measurement results should be compared with the parameters on the panel. If it is found that there is a significant difference between the value measured in this measurement and the value recorded last time, try to find out and record what kind of new load (the size, type and installation location of the load) has been added. Connected to the output of the UPS or removed from the user's load bus.

(3) If there is any obvious deviation from the measured power supply operating parameter values in the past, but no reasonable reason can be found, contact the UPS manufacturer's after-sales service department for technical support.

3. Annual inspection

In addition to the thorough cleaning and descaling of the UPS once a year, it is necessary to cut off the power to check the UPS power supply if necessary.

(1) Check whether there is voltage at the AC input terminal, battery pack input terminal and UPS input terminal to confirm that the UPS has been placed in a complete power-off state (systems equipped with bypass voltage stabilizing devices) , Also check the input terminal of the AC bypass power supply).

Since the UPS three-phase main input terminal has filter capacitors, there is a lethal high voltage between the terminals after the power is off, and they should be discharged one by one. After checking and confirming that there is no power, operate and reinforce it.

(2) Open the safety door on the UPS cabinet and check whether the internal parts of the UPS are in good condition.

(3) Carefully check the power drive components and printed circuit plug-in boards in the UPS, and pay special attention to the following components.

1) Electrolytic capacitor: Check for leakage, "topping" and swelling.

2) Transformer coils and connecting parts and chokes: Check whether there is overheating, discoloration and delamination, etc., and make sure that all power cable fastening ends are firmly connected.

3) Cables and terminals: Check whether the cable sheath has cracks, slags, scratches and damages. Check whether all the plug-ins on the printed circuit board are in firm and reliable contact, and whether the cable connection between the boards is abnormal.

4) Check the integrity of all power fuses and whether they are firmly installed.

5) Printed circuit: check the cleanliness of all circuit boards and the integrity of the circuit, check the bypass, rectifier and inverter control power supply board components for abnormal phenomena.

(4) If any signs of deterioration or performance deterioration are found, the circuit board should be replaced or necessary maintenance.

1) Use a vacuum cleaner to clean the various parts of the UPS machine or use a blower that provides a low-pressure air flow to remove any foreign residues and dust.

2) Reconnect the power supply and follow the normal operation steps to switch the UPS to the inverter power supply channel.

3) If it is possible to disconnect the AC power input switch located in the UPS input power distribution cabinet, put the UPS in the load operation state and check whether the backup time of the battery pack is within the specified range. When the terminal voltage of the battery pack drops to 40-50V higher than the critical shutdown voltage of the battery pack, immediately turn off the AC input switch (when the terminal voltage of the battery pack drops to its preset low battery voltage, the automatic shutdown voltage is too low , The UPS inverter will stop power supply, and automatically switch the load to the AC bypass power supply channel. This kind of experiment is used to detect the actual backup power supply time of the battery pack.

4. Maintenance of battery

Our unit uses imported batteries, which are valve-regulated sealed maintenance-free batteries, which are generally considered maintenance-free. Therefore, the maintenance of the battery is only limited to ensuring that the working environment temperature of the battery is controlled at 20-25°C and in a clean and dry working environment as much as possible.

However, from the analysis of the UPS failure of the chemical and electrical maintenance, the battery should be strictly maintained. This is because the float voltage and discharge voltage in the UPS power supply have been adjusted to the rated value at the factory, and the discharge current increases with the increase of the load. The load should be adjusted reasonably during use.

However, because UPS is connected to AC power for a long time, in an environment with high power supply quality and few AC power outages, the battery will be in a floating state for a long time. Shorten the service life.

Therefore, in general, the AC power should be completely cut off every 2 or 3 months and the battery should be inspected; and the battery should be fully charged and discharged every two years. The discharge time can be determined according to the capacity and load of the battery, and the battery should be recharged for more than 8 hours as required. According to the design life of the battery, strengthen its condition monitoring and replace it regularly.